this element is the only element that is shiny, mallable, and a good conductor of heat and electricity. it has a higher number atomic number than cesium but lower than radon

I do not have my reference table out to see the periodic table but in order to achieve the answer pull out the periodic table. You now know that this element is going to be a metal because it is a good conductor of electric and is malleable. Next you will find both cesium and radon and look in between them to see which one is a metal that has an atomic number that lies between both radon and cesium